Stents are cylindrical devices that are radially expandable to hold open a segment of a vessel or other anatomical lumen after deployment in the lumen. Various types of stents are in use, including balloon expandable and self-expanding stents. Balloon expandable stents generally are conveyed to the area to be treated on balloon catheters. A self-expanding stent is conveyed to a treatment site while compressed within a sheath. Once positioned, the sheath is retracted, allowing expansion of the stent.
The sheath may be retracted using a pullwire that extends from the proximal end of the stent delivery system (the end nearest the treating clinician) to the distal end of the system. In prior art systems in which the stent delivery system is guided to the desired treatment area over a guidewire, either the guidewire or the pullwire has been positioned off-center within a catheter. An off-center guidewire increases the difficulty of tracking a catheter over the guidewire. An off-center pullwire can cause a portion of the catheter to turn (to be pulled into a curved configuration) as the off-center pullwire is retracted, potentially displacing the catheter within a vessel.
Positioning multiple pullwires within a catheter such that the pullwires balance one another eliminates the problem of the catheter being pulled into a curved configuration. However, multiple pullwires held rigidly by a handle such as is typically used to retract a sheath can stiffen the catheter so that it is no longer adequately flexible to be delivered to many treatment sites.
Therefore, it would be desirable to have an improved stent delivery system that overcomes the aforementioned and other disadvantages